The invention relates in general to input systems wherein a human operator loads input data into a computer. In particular the present invention is concerned with means to provide the human operator with a positive signal or indication that the computer is receiving and recording his data.
In the building construction trades there is a necessity to provide accurate estimates of the cost of construction of new buildings for use in competitive bidding. Since the provision of an accurate cost estimate must take into account the costs of a vast multitude of structural, plumbing, electrical, and other types of purchased equipment, preparing accurate estimates of the costs of such purchased equipment has in the past been a time-consuming and expensive task. The difficulty and expense of estimating have in recent times been aggravated by a manyfold increase in the types and sizes of equipment used in modern construction, and by rapidly changing prices.
Accordingly, general and special purpose computers have come into use in order to adequately store and process the voluminous data required in the preparation of cost estimates. Such computers can easily store the pertinent data concerning a wide range of equipment from manufacturers' catalogues and provide ready access to the information on demand. Furthermore, the mathematical operations required in producing a tabulation of all of the purchased equipment for a large construction job, together with any desired cost breakdown of the materials can easily be performed by the computer.
Nevertheless human operators are required to load the data from the architects' drawings for any given project into the computer in order that it may produce the desired cost estimate. Accordingly in preparing a cost estimate using such a computer system, the estimator must work from blueprints or architects' drawings and insert quantity data for each type of purchased equipment involved. Thus, the operator manually inserts data relating to the number of feet of electrical conduit in the system or the total number of pipe fittings of a given type and size, etc.
Such information can conveniently be inserted into the computer by means of one or more of various types of probes which are electrically connected to the computer and which the operator can hold in his hand as he works on the blueprints. Such probes when manually applied to the drawing produce a signal which is indicative of the quantity data for each category of equipment involved.
Since the insertion of data by this technique involves a certain number of manual operations by the human operator there is always the possibility that, through a fault in the probe, or improper use of the probe on the drawing the data will fail to be inserted into the computer. Furthermore there is the possibility that through improper operation of the computer the operator will attempt to insert information when the computer is not in a condition to receive that information. Finally, lack of any indication from the computer that it is correctly receiving the information being provided by the human operator can often cause apprehension in the mind of the operator and consequently needless rechecking of controls, switches, etc. to be sure that the system is in the correct operative state.